Buggy code:
public class ExternalAnnotationUtil { public static final char NULLABLE = '0' ; public static final char NONNULL = '1' ; public static enum MergeStrategy { REPLACE_SIGNATURE , OVERWRITE_ANNOTATIONS , ADD_ANNOTATIONS ; } public static String extractGenericSignature ( IMethodBinding methodBinding ) { } public static String insertReturnAnnotation ( String methodSignature , char annotation , ExternalAnnotationUtil . MergeStrategy mergeStrategy ) { } public static String insertParameterAnnotation ( String methodSignature , int paramIdx , char annotation , ExternalAnnotationUtil . MergeStrategy mergeStrategy ) { } public static IFile getAnnotationFile ( IJavaProject project , ITypeBinding type , IProgressMonitor monitor ) throws CoreException { } public static void annotateMember ( IType type , IFile file , String selector , String originalSignature , String annotatedSignature , ExternalAnnotationUtil . MergeStrategy mergeStrategy , IProgressMonitor monitor ) throws IOException , CoreException { } private static String insertAt ( String signature , int position , char annotation , ExternalAnnotationUtil . MergeStrategy mergeStrategy ) { } private static String addAnnotationsTo ( String newSignature , String oldSignature , ExternalAnnotationUtil . MergeStrategy mergeStategy ) { StringBuffer buf = new StringBuffer ( ) ; assert ( newSignature . charAt ( 0 ) ) == '(' : "signature<seq2seq4repair_space>must<seq2seq4repair_space>start<seq2seq4repair_space>with<seq2seq4repair_space>'('" ; assert ( oldSignature . charAt ( 0 ) ) == '(' : "signature<seq2seq4repair_space>must<seq2seq4repair_space>start<seq2seq4repair_space>with<seq2seq4repair_space>'('" ; buf . append ( '(' ) ; SignatureWrapper wrapperNew = new SignatureWrapper ( newSignature . toCharArray ( ) , true ) ; wrapperNew . start = 1 ; SignatureWrapper wrapperOld = new SignatureWrapper ( oldSignature . toCharArray ( ) , true ) ; wrapperOld . start = 1 ; while ( ( ! ( wrapperNew . atEnd ( ) ) ) && ( ! ( wrapperOld . atEnd ( ) ) ) ) { int startNew = wrapperNew . start ; int startOld = wrapperOld . start ; if ( ( wrapperNew . signature [ startNew ] ) == ')' ) { if ( ( wrapperOld . signature [ startOld ] ) != ')' ) <START_BUG> throw new IllegalAccessError ( ( ( ( "Structural<seq2seq4repair_space>difference<seq2seq4repair_space>between<seq2seq4repair_space>signatures<seq2seq4repair_space>" + newSignature ) + "<seq2seq4repair_space>and<seq2seq4repair_space>" ) + oldSignature ) ) ; <END_BUG> startNew = ++ ( wrapperNew . start ) ; startOld = ++ ( wrapperOld . start ) ; buf . append ( ')' ) ; } int endNew = wrapperNew . computeEnd ( ) ; int endOld = wrapperOld . computeEnd ( ) ; int lenNew = ( endNew - startNew ) + 1 ; int lenOld = ( endOld - startOld ) + 1 ; if ( lenNew == lenOld ) { switch ( mergeStategy ) { case OVERWRITE_ANNOTATIONS : buf . append ( wrapperNew . signature , startNew , lenNew ) ; break ; case ADD_ANNOTATIONS : buf . append ( wrapperOld . signature , startOld , lenOld ) ; break ; default : JavaCore . getJavaCore ( ) . getLog ( ) . log ( new Status ( IStatus . ERROR , JavaCore . PLUGIN_ID , "Unexpected<seq2seq4repair_space>value<seq2seq4repair_space>for<seq2seq4repair_space>enum<seq2seq4repair_space>MergeStrategy" ) ) ; } } else if ( lenNew > lenOld ) { buf . append ( wrapperNew . signature , startNew , lenNew ) ; } else { buf . append ( wrapperOld . signature , startOld , lenOld ) ; } } return buf . toString ( ) ; } private static void writeFile ( IFile annotationFile , StringBuffer head , String annotatedSignature , String nextLines , BufferedReader tailReader , IProgressMonitor monitor ) throws IOException , CoreException { } private static void createNewFile ( IFile file , String newContent , IProgressMonitor monitor ) throws CoreException { } private static void ensureExists ( IContainer container , IProgressMonitor monitor ) throws CoreException { } }

Fix:
throw new IllegalArgumentException ( ( ( ( "Structural<seq2seq4repair_space>difference<seq2seq4repair_space>between<seq2seq4repair_space>signatures<seq2seq4repair_space>" + newSignature ) + "<seq2seq4repair_space>and<seq2seq4repair_space>" ) + oldSignature ) ) ;